Frontend for validation

[ageorgou]

Required for #3.

• [x] Button
• [x] Icon
• [x] Collect all information to create request
  • [x] Filename of ATF being edited
  • [x] Content of text area/s (there might be more than one if there's a split area for the arabic text in the future)
• ~[ ] Deal with exception (no file being opened, bad filename, file not saved, etc.)~ (moved to #37)